Mark `MemoryRange::as_slice()` and `MemoryRange::as_slice_mut()` as
unsafe.
This is due to the fact that not all representable types can be cast to
an arbitrary value. For example, if Process A sends random values to
Process B, then Process B casts the memory to a slice of `bool`, then
any values that are not 0 or 1 are undefined.
Because these functions can leak UB into the program, they are marked as
unsafe.
This patch adds `unsafe {}` blocks to all instances where this function
is called. Additionally, all instances have been checked to verify that
they do not cast to any invalid types -- most use `u8` or `u32`.
Additionally, the long-deprecated `MemoryRange::from_parts()` call was
removed, since that causes UB without being marked as unsafe.
Signed-off-by: Sean Cross <sean@xobs.io>
default system font can be statically changed by modifying
the SYSTEM_STYLE constant.
This of course will lead to a request for a dynamically
configurable preference for font size. However, early
on it was decided this is a bad idea. Here's why.
We don't provide for dynamic system-wide font selection
because this adds a lot of complexity to what would otherwise
be static code: this is a deliberate choice to improve code
density and performance. If the system font were dynamically
adjustable, then every character rendered we would potentially
have to query the PDDB for the current system font setting.
The impact of this could be mitigated by caching values but
then what happens when you actually change the font? now
you need a registry to fire messages off to all dependent
crates with cached values to flush their caches and redraw
(or you punt and force a reboot if you change font sizes,
but still, you're creating a dependency on a lot of plumbing
for even the simplest crates).
Plus, with a static font selection, the compiler can take constants
like the font height and compose them with other fitting
parameters into optimized load/stores of borders and spacings
for the static case; if you make it dynamic, all those multiplies,
adds and divides now get pulled into the main rendering loop
and are recomputed all the time. For example, if you have a static
const list of items that need to be rendered, even if the code to
compute the height of the list is written as a for loop, the compiler
will know the list is constant, and the font height is constant,
and it can condense that all into a single number at compile time,
eliminating all the code for the for loop.
If you leave the option open to change that, that entire piece
of code has to be generated and executed even though in practice
nobody changes the parameter.
StifledCertificateVerification::verify_server_cert() will verify the certificate with the default rustls WebPkiVerifier, BUT specifically override a `CertificateError::UnknownIssuer` and return ServerCertVerified::assertion()
This allows us to use rustls to open a tls connection to a host with an untrusted certificate chain. And subsequently get to see the certificate chain, and possibly choose to trust the chain, or links in it.
This change is made with the intention of making the xous-rs crate a bit
more freestanding without depending on the xtask build system.
Signed-off-by: Jean-Pierre De Jesus DIAZ <me@jeandudey.tech>
